Our Field Sales Agronomists are seeing soybean aphid populations growing. Currently, we are seeing them near wooded areas in the northwestern portions of our territory. This is favorable aphid weather, so we anticipate population growth.
Soybean aphids can harm yield potential, and populations can double in just a few days. They tend to show up during late vegetation-R5 stage, causing damage by sucking plant sap. Soybean aphid outbreaks are associated with a reduction in plant height, pod number, seed size and quality, and yield. Symptoms of feeding damage may include plant stunting, and/or leaves covered with honeydew (the sticky substance excreted by aphids) and black sooty mold, a fungal growth on honeydew-coated leaves.
Our team starts spot-checking seedling soybean and continue checking through pod fill. Look for these aphids on growing points and young leaves. As soybean plants mature from late vegetative through reproductive stages, check for soybean aphids on all plant parts. Although most common on undersides of leaves, they also occur on stems, petioles, and upper leaf surfaces.
Insecticide application timing is crucial. Use an action threshold of 250 aphids per plant. This action threshold should be based on an average of aphids per plant over 20-30 plants sampled throughout the field.
When you are trying to decide if you should spray or not, make sure you are looking at the pre-harvest intervals, as we hit late August we will want to make sure we are following the label. We will continue to monitor the situation and keep you updated. Please make sure you reach out to your local FSA with any questions you have. We have sprayers at the ready if aphids could negatively impact your bottom line.